The USS Arleigh Burke (DDG 51) Class destroyer represents the latest in a distinguished lineage of combatants designed and developed by the U.S. Navy. It is one of the world's finest hull forms, optimizing speed, power, seakeeping, stability, and payload capacity, even though its initial design dates back nearly three decades. Since the first-of-class DDG 51 became operational in 1991, the hydrodynamic community has unveiled numerous advances in ship technology and design. The advances are applicable, not only to DDG 51 class ships, but also to other large hull ship forms, military and non-military.
The technological improvements were developed to enhance the operational performance and/or to foster reductions in operating and life cycle total ownership costs. The technological improvements include changes in propeller design, the addition of bow and stern end bulbs, and stem flaps, and improved rudder design. Cleaning techniques for cleaning the hull and propellers have also been developed to prevent increase in power and loss of propeller efficiency.
Stern flaps are extensions of the hull bottom surface created by a relatively small appendage welded to the transom of the ship. Stern flaps are known in the art, and have been proven during sea trials to reduce propulsive power, and to foster significant fuel cost savings, while increasing both ship endurance and top speed. The U.S. Navy has obtained several patents for stem flaps, such as, U.S. Pat. No. 6,038,995, U.S. Pat. No. 6,698,370 and U.S. Pat. No. 6,745,715. A stern flap based on U.S. Pat. No. 6,038,995, which could be retrofitted behind the transom wedge was successfully installed on all 28 Flight I and II hulls, DDG 51 through DDG 78.
Regarding the stern end bulbs, it is acknowledged that a ship moving in water generally creates a much larger bow wave than a stern wave. Thus, the most logical location for a bulb is at the bow because the large energy content in the bow wave is a potential source of more recoverable energy. Nevertheless, the stern end of the ship also generates waves that are a source of “wasted” energy. In contrast to the plethora of technical reports on bow bulb design and their universal and widespread usage at sea, there are only a few dozen technical reports and rare full scale applications of stern end bulbs. In order to be employed, it is desired that the stern end bulb design overcomes already enhanced performance with the existing stern flap.
Both stern flaps and stern end bulbs interact with the hull to produce a wave system that reduces the total wave resistance. In addition, the stern flap also reduces after-body resistance. For either body to be effective the drag reduction due to interactions with the hull resistance must be greater than the inherent drag of the device itself. The authors of this patent application have illustrated stern bulb/flap combinations conceptually in non-patent literature presentations, “Hydrodynamic Energy saving Enhancements for DDG 51 Class Ships” and “Stern End Bulb for Energy Enhancement and Speed Improvement”. Apart from these conceptual illustrations, there is no prior art teaching of a stern end bulb and flap combination that is properly constructed to achieve the goals of reducing resistance on the hull, whilst avoiding the adverse effects of its structure.
In addition to improving the ship efficiencies as it relates to fuel consumption, it is also important to maintain efficiency while performing other mission related tasks. The USS Arleigh Burke (DDG 51) Class destroyer or other water vessels may perform other tasks related to monitoring the environment. This may involve the use of monitoring devices including, but not limited to, unmanned surface vehicles (USVs), unmanned underwater vehicles (UUVs), or towed arrays. The deploying of these sea-monitoring devices, and in the case of USVs and UUVs, the launching and recovering creates technical challenges that must be met. Some techniques for deployment may involve the use of davits or other lifting apparatuses for lifting the monitoring devices from the deck of the water vessel into the water below. Ramps may also be employed for lowering the monitoring devices into the water.
For more direct access to the water, some water vessels employ sea-level openings in their hulls through which the monitoring devices, such as USVs and UUVs may be passed. As stated above, the USS Arleigh Burke (DDG 51) Class destroyer has one of the world's finest hull forms, optimizing speed, power, seakeeping, stability, and payload capacity. Consequently, the addition of openings or penetrations to the hull structure may have adverse effects on vessel performance. Thus, it is desired to have a sea-level opening for launching and/or recovering monitoring devices that do not penetrate the hull or have adverse effects on vessel performance.